1. Field of the Invention
The present invention relates to an accident point locating system comprising, in combination, a digital protective control system that receives state quantities indicating a state of an electric power system, converts the state quantities into corresponding data and carries out the protective control of the electric power system, and a display system that carries out displaying and controlling operations to monitor the operation and state of the digital protective control system through a communication network.
2. Description of the Related Art
Digital protective control systems are used prevalently in the field of electric power systems. The functions of digital protective control systems have been advanced in recent years by the employment of high-performance microprocessors and large-capacity memories. More concretely, digital protective control systems include protective relay systems that detect accidents in electric power systems, accident point locating systems that locate accident point in electric power systems, and system stabilizing systems that stabilizes electric power systems. The digital protective control systems are applied prevalently to the operation of electric power systems.
A conventional digital protective control system will be described. Referring to FIG. 9, a digital protective control system 1 includes an A/D conversion unit 2, a digital processing unit 3, an I/O interface 4 connected to an external device, such as a circuit breaker, and a bus 5. Those components are interconnected by the bus 5.
The A/D conversion unit 2 includes analog filters 6-1 to 6-n, sample-and-hold circuits 7-1 to 7-n, a multiplxer 8 and an A/D converter 9. The A/D conversion unit 2 receives n pieces of analog information A-1 to A-n representing state data on the state of an electric power system to be protected and controlled, such as current and voltage, samples the n pieces of analog information A-1 to A-n at predetermined sampling intervals, holds sampled analog state data and converts the analog state data into corresponding digital state data.
The digital processing unit 3 includes a CPU 10, a RAM 11, a ROM 12, and an EEPROM (electrically erasable programmable read-only memory) 13. The digital state data is transferred sequentially to the RAM 11. The CPU 10 carries out various protective operations including a relay operation by using the digital state data stored in the RAM 11 and set values for a protection relay stored in the EEPROM 13 according to programs stored in the ROM 12.
The I/O interface 4 receives information about external controllers including information about a circuit breaker and gives output signals including a signal requesting the operation of the protection relay, a reset signal and a trip command to external devices. The display 14 is a human interface that displays the state and operating condition of the digital protective control system.
An accident point locating system uses an accident point locating algorithm for calculating the distance between a control station and an accident point by using data provided by the A/D conversion unit in the ROM 10 and gives data on the distance between the control station and the accident point to the display 14. Practically used accident point locating algorithms include those of an impedance calculating system that use only data available from the own control station, and those of a positive-phase loop locating system that uses electrical quantity data available from the own control station and those available through special transmission lines from other control stations. A concrete algorithm transmission line system for locating operations is described in, for example, Japanese Pat. Application No. Hei 7-64729 (JP-A No. Hei 8-233895) made by the applicant of the present patent application.
The social importance of the electric power system has increased in recent years. The electric power system requires considerable labor for maintenance and operation. For instance, when an accident occurs in a power transmission line, an accident point where the accident occurred must be located and the condition of equipment relating to the accident point must be quickly confirmed. An accident point locating system is used for calculating the distance between the relevant control station and the accident point on the basis of electric quantity data at the moment the accident occurred to reduce labor for maintenance and operation. However, the conventional accident point locating system composed of hardware equivalent to a digital protective control system is expensive. Since the display for displaying the results of accident point locating operations is able to display limited information, such as the distance between the control station and the accident point and a phase in which the accident occurred. Consequently, the output of the accident point locating system must be checked against a power transmission system map showing the layout of power transmission lines to locate the accident point.
Accordingly, it is a first object of the present invention to reduce special hardware and to reduce the cost by carrying out accident point locating operations by an display operating apparatus, such as a personal computer. A second object of the present invention is to provide a highly reliable accident point locating system capable of automatically indicating an accident point on a map by checking the results of accident point locating operations against geographic map information and power transmission line map information, of reducing load on operation and maintenance personnel and of being easily operated.
To achieve the object, according to a first aspect of the present invention, an accident point locating system is provided, which includes: a plurality of digital protective controllers that receive state data representing a state of an electric power system, convert the state data into corresponding digital state data and execute an electric power system protecting control, each of the digital protective controllers having an absolute time acquiring means for acquiring an absolute time, an A/D converting means for sampling the state data at a predetermined sampling period at absolute times acquired by the absolute time acquiring means and converting the sampled state data into corresponding digital state data, a state data processing means for deciding whether any malfunction occurred in equipment to be protected on the basis of the digital state data provided by the A/D converting means, a state decision means for executing a malfunction decision function other than the malfunction decision function of the state data processing means on the basis of the digital state data provided by the A/D converting means to decide whether or not any malfunction occurred in the equipment to be protected and in the vicinity of the equipment, a recording means for adding absolute sampling time to the digital state data provided by the A/D converting means and recording the digital state data with the absolute time when the state decision means decides that a malfunction occurred in the equipment to be controlled and protected or in the vicinity of the equipment, and a digital data sending means for reading the digital state data with the absolute time from the recording means and providing the same on a communication network; and a display operating system that is connected to the plurality of digital protective controllers by the communication network and executes displaying operations to monitor the operation and condition of the digital protective controllers, the display operating system having a digital state data receiving means connected to the communication network to receive a plurality of digital state data with the absolute time through the communication network, distance calculating means for calculating the distance between the control station and an accident point by using the plurality of digital state data with the absolute time received by the digital data receiving means, and a display means for displaying the output of the distance calculating means.
According to the present invention, the display operating system receives the digital state data with the absolute time provided on the communication network by the digital protective control system and executes operations for accident point location. The operations for accident point location can be carried out by the display operating system comprising a personal computer or the like, special hardware can be reduced and the cost can be reduced.
Preferably, the accident point locating system further comprises a recording unit connected to the communication network and comprising a receiving means for receiving the digital state data with the absolute time provided by the digital protective controllers, a storage means for storing the received digital state data, a program module storage means for storing an accident point locating program module specifying accident point locating operations, and a sending means for sending out the digital state data with the absolute time stored in the storing means and the accident point locating program module stored in the program module storage means; wherein the display operating system further comprises a requesting means for requesting the recording unit to give the same the digital state data with the absolute time and the accident point locating program module, the receiving means of the display operating system is capable of receiving the digital state data with the absolute time and the accident point locating program module requested by the requesting means, and the distance calculating means of the display operating system is capable of executing the accident point locating program module on the basis of the digital state data with the absolute time received by the receiving means of the display operating system.
The digital state data with the absolute time of occurrence of the accident and the accident point locating program module are stored in the storage means of the accident point locating system, the digital state data with the absolute time and the accident point locating program module are down-loaded into the display operating system, such as a personal computer, the accident point locating program module is executed by the display operating system, and the unitary management of the digital state data with the absolute time and the accident point locating program module can be easily achieved.
Preferably, the display operating system further includes a power transmission line map data storage means for storing power transmission line map data, and checking means for checking the output of the accident point locating means representing the distance between a control station and an accident point against the power transmission line map data, and the display means has a function to display the accident point on the power transmission line map data on the basis of the result of checking by the checking means.
The accident point locating system thus constructed is capable of checking the result of the accident point locating operations against the power transmission line map data and of indicating the accident point on the map with reliability. Preferably, the display operating system includes a phenomenon discriminating means that decides that a plurality of digital state data with the absolute time received from the plurality of digital protective controllers in a predetermined time period are those on a single phenomenon on the basis of a time-dependent causal relationship between the digital state data provided by the plurality of digital protective controllers.
Since the digital state data with the absolute time are handled as a single data on the basis of the time-dependent causal relationship between the digital state data provided by the plurality of protective controllers, data to be used for accident point locating operation can be automatically determined.